Gastrointesitinal Stromal Tumor

Case History: A 57-year-old woman presented complaining of a long lasting epigastric pain. The pain was irregular, vague without spreading or progression or correlation to alimentary habit. She had no nausea or vomiting, neither hematemesis nor hematochezia. She did not report any change in her bowel habit and had not experienced any recent fevers. She denied any history of alcohol consumption, cigarette smoking, non-steroid anti-inflammatory medications intake and weight loss. Her past medical history and previous routine abdominal ultrasound check were unremarkable.

On physical examination, her heart rate, blood pressure, respiratory rate and body temperature were normal. The cardiovascular and respiratory findings are unremarkable. There is little to no tenderness to palpation in the upper abdomen. Neither bowel distension nor abnormal motility was noticed. Auscultation of bowel sound revealed normal. General blood and urine tests were in normal range. Abdominal ultrasound and CT scan findings showed an intramural gastric tumor, which is very suggestive of GIST. A subtotal gastrectomy was performed and the diagnosis of low-grade GIST was confirmed (CD117 +, CD34+, Desmin -). The patient is currently undergoing surveillance.

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Figure 1:  Abdominal ultrasound showed a homogenous hypoechogenic mass located within the posterior gastric wall, protruding into the inner lumen. The mass was oval in shape, had regular and distinct margin without infiltration. There was no gastric wall thickening and the layers remained intact. No evidence of hypervascularity on Color Doppler ultrasound of the mass.

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Figure 2: Gastric endoscopy: a submucosal mass was found in the gastric antrum which is ovoid in shape, smooth protruding into the lumen. The mucosal layer remained intact. The mass was relatively firm on compression.

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Figure 3: Axial contrast-enhanced computed tomography (CECT) showed a well-defined, ovoid, homogeneous, intramural mass arising from the gastric antrum with slightly enhancement. The mass was measured 2 cm in diameter. There was no evidence of adjacent tissue infiltration or lymphadenopathy or ascites. CT scan findings were suggestive of a gastric GIST.

Diagnosis: Gastrointestinal stromal tumor (GIST)

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Figure 4: Gross section showed a submucosal tumor located in the pyloric antrum which is firm and fleshy in nature. The mucosal surface remained intact.

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Figure 5:  Histopathology HE staining x 400. Tumor cells are fusiform in shape, with vacuolated cytoplasm and arrayed palisade.

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Figure 6:  Immunohistochemical staining x 400. CD117+, brown-yellow membrane staining.

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Figure 7: CD34+

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Figure 8: Desmin -

Discussion: Gastrointestinal stromal tumors (GISTs) are currently the most common mesenchymal tumors of the gastrointestinal tract, with an estimated 4500-6000 new cases reported each year in the United States. The incidence of GIST is estimated to be approximately 10-20 cases/million/year. Malignant possibility is 20 percent to 30 percent. A few estimates and studies indicate the incidences of approximately 14.5 cases/million/year in Sweden, 14.2 in Northern Italy, 13.7 in Taiwan, 12.7 in Holland, 11 in Iceland and 6.5 in Norway. Recent report shows an incidence of 6.8/million from 1992-2000 in the United States [2]. However, the precise incidence of GISTs is still unknown because of the incomplete definition and classification. Over 90 percent of GISTs occur in adults over 40 years old, in a median age of 63, though GISTs have been reported in all ages, including children. No difference in prevalence between sexes. There are no elements that indicate any association with geographic location, ethnicity, race or occupation [3].

Clinical manifestation of GIST is erratic. Seventy percent are symptomatic at presentation, 20 percent are asymptomatic and 10 percent are detected at autopsy. Common presentations include vague abdominal pain, palpable mass, gastrointestinal bleeding, fever, anorexia, weight loss and anemia [1].

Ultrasound may identify GISTs fortuitously, especially if they are large, so that other imaging tests can be performed to confirm the diagnosis. Echoendoscopy can be used to study the esophagus, gastric or rectal tumors to determine local extension. During this procedure, cytopuncture or biopsy can be performed [5]. Computed tomography (CT) is frequently the imaging technique used in the first intention in case of suspected GISTs and CT is also the standard imaging method in patients with GISTs. CT has a high reliability in tumor detection and staging and has been established as the standard method for assessing therapy response. Indeed, CT is considered to be the reference examination for the local study of these tumors and for tumors extension. GISTs usually present as well circumscribed exoluminal masses of different size.

Although surgical resection is the treatment of choice for the primary GISTs, recurrence occurs in most patients, even after a complete resection with tumor-free margin. The median time to recurrence after operation is approximately two years. The main goal of imaging is surveillance to detect recurrence of progression as early as possible. Recurrences typically occur first in the liver of peritoneum. Traditional criteria for progression include tumor size increase, development of new lesions and metastasis [4]. Imatinib and sunitinib were found to be able to potently inhibit the tyrosine kynase activity of KIT [8]. The specific identification of GIST has become more important after the availability of Kit-selective tyrosine kinase inhibitor Glivec, especially in the treatment of high risk, unresectable and metastatic tumors.

References
1. Roy et al. Spontaneous perforation of jejuna Gastrointestinal Stromal Tumour (GIST). Case report and review of literature, World Journal of Emergency Surgery 2012, 7:37
2. Xiaohui Zhao, Changjun Yue. Gastrointestinal Stromal Tumor, J GastroIntest Oncol 2012; 3 (3): 189-208.
3. Stamatakos et al. Gastrointestinal Stromal Tumour: review. World Journal of Surgical Oncology 2009, 7:61.
4. Xie Hong, Haesun Choi, Evelyne M. Loyer, Robert S. Benjamin, Johnathan C. Trent, Chusilp Charnsangavej. Gastrointestinal stromal tumor: role of CT in diagnosis and in response evaluation and surveillance after treatment with Imatinib, Radiographics 2006, 26 (2): 481-495
. 5. Bensimhon D. et al. Imaging of Gastrointestinal Stromal Tumors. J Radiol 2009; 90: 469-480, Elsevier Masson
6. Christopher B. Tan et al. Gastrointestinal Stromal Tumors: a review of case reports, diagnosis, treatment, and future directions. ISRN Gastroenterology 2012.
7. Stattaus J. Consensus report on the radiological management of patients with Gastrointestinal Stromal Tumors: recommendation of the German GIST imaging work up. Cancer Imaging 2012 (12), 126-135
8. Lamba et al. Recent advances and novel agents for Gastrointestinal Stromal Tumors. Journal of Hematology and Oncology 2012, 5:21